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A New particle to explain lithium-7 big bang prediction

  1. Jul 11, 2016 #1
    A light particle solution to the cosmic lithium problem
    Andreas Goudelis, Maxim Pospelov, Josef Pradler
    (Submitted on 29 Oct 2015 (v1), last revised 24 May 2016 (this version, v2))
    We point out that the cosmological abundance of 7Li can be reduced down to observed values if during its formation Big Bang Nucleosynthesis is modified by the presence of light electrically neutral particles X that have substantial interactions with nucleons. We find that the lithium problem can be solved without affecting the precisely measured abundances of deuterium and helium if the following conditions are satisfied: the mass and lifetimes of such particles are bounded by 1.6MeV≤mX≤20MeV and few100s≲τX≲104s, and the abundance times the absorption cross section by either deuterium or 7Be are comparable to the Hubble rate, nXσabsv∼H, at the time of 7Be formation. We include X-initiated reactions into the primordial nucleosynthesis framework, observe that it leads to a substantial reduction of the freeze-out abundances of 7Li+7Be, and find specific model realizations of this scenario. Concentrating on the axion-like-particle case, X=a, we show that all these conditions can be satisifed if the coupling to d-quarks is in the range of f−1d∼TeV−1, which can be probed at intensity frontier experiments.
    Comments: 5 pages, 4 figures; v2: minor improvements, matches published version
    Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
    Journal reference: Phys. Rev. Lett. 116, 211303 (2016)
    DOI: http://arxiv.org/ct?url=http%3A%2F%2Fdx.doi.org%2F10%252E1103%2FPhysRevLett%252E116%252E211303&v=08290ee6 [Broken]
    Cite as: arXiv:1510.08858 [hep-ph]
    (or arXiv:1510.08858v2 [hep-ph] for this version)

    any thoughts? what are the implications of such a particle to the SM and SUSY?

    any connection with this?

    Evidence for a Protophobic Fifth Force from 8Be Nuclear Transitions
    Jonathan L. Feng, Bartosz Fornal, Iftah Galon, Susan Gardner, Jordan Smolinsky, Tim M. P. Tait, Philip Tanedo
    (Submitted on 25 Apr 2016)
    Recently a 6.8σ anomaly has been reported in the opening angle and invariant mass distributions of e+e− pairs produced in 8Be nuclear transitions. The data are explained by a 17 MeV vector gauge boson X that is produced in the decay of an excited state to the ground state, 8Be∗→8BeX, and then decays through X→e+e−. The X boson mediates a fifth force with a characteristic range of 12 fm and has milli-charged couplings to up and down quarks and electrons, and a proton coupling that is suppressed relative to neutrons. The protophobic X boson may also alleviate the current 3.6σ discrepancy between the predicted and measured values of the muon's anomalous magnetic moment.
    Comments: 6 pages, 2 figures
    Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    Report number: UCI-TR-2016-09
    Cite as: arXiv:1604.07411 [hep-ph]

    Feng's paper, which comes later, does not reference nor cite the earlier paper by Goudelis et al, and does not state his proposed x boson would resolve the lithium 7 big bang overabundance problem.

    Feng's xboson has right mass and lifetime and similar properties as proposed by Goudelis et al, to also reduce lithium 7 big bang overabundance problem.

    Is it possible by Goudelis et al particle is the same particle as Feng's 17 mev Xboson?
     
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Jul 12, 2016 #2

    malawi_glenn

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    I think that the paper by Goudelis et al discusses an axion-like particle whereas Feng et al have a particle which mediates a new 5th force (which is not felt by the protons)

    It would be interesting to see if Feng et al could try to calculate the big bang nuclear synthesis of the elements, as a constraint on their particle
     
  4. Jul 12, 2016 #3
    which do u think is more plausible? or do you think both particles an axion-like and feng's boson both exist at or near same mass 17 mev
     
  5. Jul 13, 2016 #4

    malawi_glenn

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    I have no idea, particle cosmology is not my specialty.

    And in physics, we don't believe we do experiments!
     
  6. Jul 13, 2016 #5

    ohwilleke

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    A priori, neither is very plausible. The vast majority of anomalous experimental results do not, in the end, require that one postulate a new particle or a new set of laws of physics.

    The cosmic lithium problem has been addressed with many much more plausible approaches to interpreting the experimental data and applying the existing laws of physics in slightly different ways than those that create the appearance of a "cosmic lithium problem" (e.g. by determining that a path by which lithium of the appropriate isotype may be created that was ignored in other calculations is more important than believed for previously unrecognized reasons).

    An anomaly in nuclear transitions of 8Be, similarly, is far more likely to do with a problem with our model of the 8Be atom, which is not something that has been calculated from first principles using QCD, than it is to be due to a fifth force that seemingly has no other phenomenological effects. In all likelihood, the model that gives rise to the apparent disparity between theory and experiment assumes for mathematical simplicity that some of the particles in the composite 8Be system are independent or symmetrical in some fashion, when in fact, they are not. The quirk with 8Be is probably basically random and similar in source to the fact that Tc (element 43) is radioactive, even though most other elements with low atomic numbers are not.

    Another plausible possibility might be that the model to which a comparison has been made has not considered properly the effects of composite, Standard Model bosons (like the pions that mostly mediate the strong nuclear force), possibly virtual ones, or the "sea" of particles that make up the proton and neutron in the more sophisticated description of these particles.

    Find half a dozen comparably strong anomalies and a single fifth force explanation that can explain all of them, and you have a plausible theory. But, inventing an entire theory to explain one isolated outlier result with a new force when that force has no other observable effects (even though lots of isotypes ought to be similarly affected by any such force) makes no sense in an area where the underlying theoretical prediction isn't grounded in a rock solid way to a fundamental part of the Standard Model. Honestly, it comes across as a lazy de ex machina solution to a problem that almost surely has a more difficult to reach answer.

    If there was a hydrogen or helium anomaly, i.e. a 6.8 sigma anomaly in a simple system that has been modeled from first principles with QCD, I'd take it much more seriously (see, e.g., the muonic hydrogen radius issue).
     
    Last edited: Jul 13, 2016
  7. Jul 13, 2016 #6
    suppose there is a Goudelis-Feng particle with these properties

    mass of 17 MeV and 100s≲τX≲104s mediating fifth force with a characteristic range of 12 fm coupling to d-quarks is in the range of f−1d∼TeV−1 milli-charged couplings to up and down quarks and electrons, and a proton coupling that is suppressed relative to neutrons


    the papers hypothesis this particle to explain
    lithium-7 overabundance
    nuclear transitions of 8Be
    muon's anomalous magnetic moment

    that's 3 anomalous results explained with 1 hypothetical particle

    suppose there is a Goudelis-Feng particle mediating a fifth force

    what would its effects be on the muonic hydrogen radius issue

    - perhaps that is a paper that has yet to be written

    what would such a particle and fifth force have on dark matter?

    what would such a particle and fifth force have on higgs hiearchy to the QCD strong cp problem ?
     
    Last edited: Jul 13, 2016
  8. Jul 13, 2016 #7
    what about SUSY? how would it effect gauge coupling unification if there is a fifth force as described in the papers
     
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